There are at least 2 million functionally deaf individuals in the United States, and an estimated 53 million worldwide. Auditory perception is an important part of an individual's integration into society because much of a person's interactions with other people and electronic and mechanical devices is through audible information. For deaf individuals, conversing with friends and family, interacting with mobile devices, watching television, and hearing cars and other nearby machinery can be difficult or impossible. Without auditory perception, deaf individuals face operational difficulties, entertainment difficulties, and safety difficulties.
One conventional tool available for deaf individuals is the cochlear implant. However, cochlear implants (CI) are not a viable hearing solution for a large fraction of the deaf individuals. One reason is cost: as a lower bound, the overall cost of a CI implantation procedure and subsequent follow-ups is $40,000. This places CIs out of economic reach for many. Additionally, CIs require an invasive surgery. Furthermore, CIs have limited benefits in early-onset deaf adults who are receiving the CI after the age of 12. Thus, not only is the CI expensive and the implantation a dangerous surgical process, but the CI must be implanted while the individual is young. This limits options for deaf individuals who seek auditory perception later in life.
The problems described above underscore the need for a low-cost, non-invasive hearing solution, and one that can work for adults who have been deaf since birth. One conventional solution is to use sound-to-touch sensory substitution devices. However, a successful sound-to-touch sensory substitution device has yet to be developed. Sound-to-touch devices as an aid for hearing have been researched in the past. However, such devices have been unable to achieve a sufficient efficacy to act as a full substitution for hearing and instead only act as a hearing “aid,” rather than as a substitution device. These devices generally rely on band-pass filtering an audio signal and playing this filtered output to the skin over vibrating solenoids. These solenoids operate at a fixed frequency of less than half the bandwidth of some of these band-passed channels, leading to aliasing noise. Thus, the touch representation of received audio sounds is inaccurate and also insufficiently accurate enough to provide a substitute for hearing the audio sounds. Furthermore, the limited bandwidth available for conveying information restricts the application of these prior sound-to-touch substitution devices to only low-bandwidth audio applications, without the ability to convey high-throughput data.